Beam transport system and particle beam therapy system

Abstract

A beam shaping device included in a beam transport system is provided with: a pre-stage quadrupole electromagnet that reduces a distribution width of x-angle components that are inclinations in the x-direction of the charged particles in the beam with respect to the traveling direction; a penumbra expander that moderates an end profile of a particle-number distribution of the x-angle components in the beam having passed through the pre-stage quadrupole electromagnet; and a post-stage quadrupole electromagnet that adjusts a betatron phase in a phase-space distribution in the x-direction, of the beam having passed through the penumbra expander; wherein the post-stage quadrupole electromagnet adjusts a phase advance angle of the betatron phase from the penumbra expander to the isocenter, to be in a range of an odd multiple of 90 degrees±45 degrees.

The invention claimed is: 
     
       1. A beam transport system which comprises a beam shaping device by which a distribution profile of a charged particle beam having, at an end in a cross-sectional direction of the beam, a steep portion where a particle number varies steeply, is shaped into a moderated form; and which transports the charged particle beam to an irradiation target that is positioned so as to include an isocenter as a positional reference for irradiation;
 wherein, assuming that a direction perpendicular to a traveling direction of the charged particle beam and passing from a center of the charged particle beam to the steep portion is an x-direction, and inclinations of charged particles forming the charged particle beam with respect to the traveling direction, are angle components, the beam shaping device comprises: 
 a pre-stage quadrupole electromagnet that reduces a distribution width of x-angle components that are the angle components in the x-direction in the charged particle beam; 
 a penumbra expander that moderates an end profile of a particle-number distribution of the x-angle components in the charged particle beam having passed through the pre-stage quadrupole electromagnet; and 
 a post-stage quadrupole electromagnet that adjusts a betatron phase in a phase-space distribution in the x-direction, of the charged particle beam having passed through the penumbra expander; and 
 wherein the post-stage quadrupole electromagnet adjusts the betatron phase so that a phase advance angle thereof from the penumbra expander to the isocenter is in a range of an odd multiple of 90 degrees±45 degrees. 
 
     
     
       2. The beam transport system of  claim 1 , wherein the pre-stage quadrupole electromagnet comprises:
 at least two quadrupole electromagnets for reducing the distribution width of the x-angle components in the charged particle beam; and 
 a quadrupole electromagnet for reducing a beam size in a y-direction that is perpendicular to the traveling direction of the charged particle beam and perpendicular to the x-direction. 
 
     
     
       3. The beam transport system of  claim 1 , further comprising a beam-profile confirmation device for confirming a beam profile, at a position where the phase advance angle of the betatron phase from the penumbra expander is an odd multiple of 90 degrees. 
     
     
       4. The beam transport system of  claim 1 , wherein the penumbra expander is a scatterer with a thickness of 0.1 mm or less. 
     
     
       5. The beam transport system of  claim 1 , wherein the penumbra expander comprises a dipole electrode;
 wherein the dipole electrode generates a periodically-varying electric field; and 
 wherein, in the electric field, a period that is large in variation is shorter than a period that is small in variation, and their frequency is 1 MHz or more. 
 
     
     
       6. The beam transport system of  claim 1 , wherein the penumbra expander comprises a dipole electromagnet;
 wherein the dipole electromagnet generates a periodically-varying magnetic field; and 
 wherein, in the magnetic field, a period that is large in variation is shorter than a period that is small in variation, and their frequency is 1 MHz or more. 
 
     
     
       7. A particle beam therapy system comprising: a beam generation apparatus that generates a charged particle beam and accelerates it up to a given energy using a synchrotron; a beam transport system that transports the charged particle beam accelerated by the beam generation apparatus; and a particle beam irradiation apparatus that irradiates the charged particle beam transported by the beam transport system to an irradiation target;
 wherein said beam transport system is the beam transport system in  claim 1 . 
 
     
     
       8. A particle beam therapy system comprising: a beam generation apparatus that generates a charged particle beam and accelerates it up to a given energy using a cyclotron; a beam transport system that transports the charged particle beam accelerated by the beam generation apparatus; and a particle beam irradiation apparatus that irradiates the charged particle beam transported by the beam transport system to an irradiation target;
 wherein said beam transport system is the beam transport system in  claim 1 , and includes a scatterer for changing energy of the charged particle beam and a collimator for limiting a beam size expanded by the scatterer, between the cyclotron and the beam shaping device; and 
 wherein the penumbra expander of the beam shaping device is placed at a position where a phase advance angle of the betatron phase from the collimator is 90 degrees. 
 
     
     
       9. The particle beam therapy system of  claim 7 , further comprising a rotary gantry for rotating the particle beam irradiation apparatus centering on the isocenter;
 wherein the penumbra expander is placed on the upstream side of the rotary gantry. 
 
     
     
       10. The beam transport system of  claim 2 , further comprising a beam-profile confirmation device for confirming a beam profile, at a position where the phase advance angle of the betatron phase from the penumbra expander is an odd multiple of 90 degrees. 
     
     
       11. The beam transport system of  claim 2 , wherein the penumbra expander is a scatterer with a thickness of 0.1 mm or less. 
     
     
       12. The beam transport system of  claim 3 , wherein the penumbra expander is a scatterer with a thickness of 0.1 mm or less. 
     
     
       13. The beam transport system of  claim 2 , wherein the penumbra expander comprises a dipole electrode;
 wherein the dipole electrode generates a periodically-varying electric field; and 
 wherein, in the electric field, a period that is large in variation is shorter than a period that is small in variation, and their frequency is 1 MHz or more. 
 
     
     
       14. The beam transport system of  claim 3 , wherein the penumbra expander comprises a dipole electrode;
 wherein the dipole electrode generates a periodically-varying electric field; and 
 wherein, in the electric field, a period that is large in variation is shorter than a period that is small in variation, and their frequency is 1 MHz or more. 
 
     
     
       15. The beam transport system of  claim 2 , wherein the penumbra expander comprises a dipole electromagnet;
 wherein the dipole electromagnet generates a periodically-varying magnetic field; and 
 wherein, in the magnetic field, a period that is large in variation is shorter than a period that is small in variation, and their frequency is 1 MHz or more. 
 
     
     
       16. The beam transport system of  claim 3 , wherein the penumbra expander comprises a dipole electromagnet;
 wherein the dipole electromagnet generates a periodically-varying magnetic field; and 
 wherein, in the magnetic field, a period that is large in variation is shorter than a period that is small in variation, and their frequency is 1 MHz or more. 
 
     
     
       17. A particle beam therapy system comprising: a beam generation apparatus that generates a charged particle beam and accelerates it up to a given energy using a synchrotron; a beam transport system that transports the charged particle beam accelerated by the beam generation apparatus; and a particle beam irradiation apparatus that irradiates the charged particle beam transported by the beam transport system to an irradiation target;
 wherein said beam transport system is the beam transport system in  claim 2 . 
 
     
     
       18. A particle beam therapy system comprising: a beam generation apparatus that generates a charged particle beam and accelerates it up to a given energy using a synchrotron; a beam transport system that transports the charged particle beam accelerated by the beam generation apparatus; and a particle beam irradiation apparatus that irradiates the charged particle beam transported by the beam transport system to an irradiation target;
 wherein said beam transport system is the beam transport system in  claim 3 . 
 
     
     
       19. A particle beam therapy system comprising: a beam generation apparatus that generates a charged particle beam and accelerates it up to a given energy using a cyclotron; a beam transport system that transports the charged particle beam accelerated by the beam generation apparatus; and a particle beam irradiation apparatus that irradiates the charged particle beam transported by the beam transport system to an irradiation target;
 wherein said beam transport system is the beam transport system in  claim 2 , and includes a scatterer for changing energy of the charged particle beam and a collimator for limiting a beam size expanded by the scatterer, between the cyclotron and the beam shaping device; and 
 wherein the penumbra expander of the beam shaping device is placed at a position where a phase advance angle of the betatron phase from the collimator is 90 degrees. 
 
     
     
       20. The particle beam therapy system of  claim 8 , further comprising a rotary gantry for rotating the particle beam irradiation apparatus centering on the isocenter;
 wherein the penumbra expander is placed on the upstream side of the rotary gantry.